Depending on how much work effort (reformatting) you want to put in
*AND* if the PDF was generated by a good PDF generator (that is one
that "respects" formatting), it may be as simple as just using Adobe
Acrobat Reader to open the PDF, select all text and paste into PPT (or
Word if you prefer). This of course assumes the PDF allows content
copying.
If that doesn't work, as others suggest find a converter.
If you're still not comfortable with the free/downloadable converters,
you could always download a trial version of Adobe Acrobat
Professional (I think its good for 60 days). Acrobat Pro does an
EXCELLENT job of reverting PDFs back into Office formats. Its not
automatic though. Open the PDF, then "Save As...", suggested formats
from there would be either .DOC, RTF or .XML. Then open that file from
PPT. A little warning here, the trial of Acrobat Pro is probably about
700MB.
HTH.